In recent years, substation facilities have had to be strengthened as the power facilities have been installed at remote places or as the supply of power to cities has increased. For these necessities, there have already been spread and serviced gas insulated devices such as so-called gas-insulated breakers or transformers in which a substation device such as a disconnector or breaker is housed in a closed container by using SF6 gas, which is excellent in insulation and arc extinguishing ability to improve the environmental adaptation and to decrease the installation volume per kVxc2x7A. This gas-insulated device is advantageous in its compactness and of its elimination of the exposed charging unit of a grounded tank, but is defective in difficulty in diagnosis for the maintenance, attributed to high performance, the increase in the time period for the maintaining and repairing works, and the marked lowering of the insulation reliability when the inside becomes abnormal. Similar problems are caused in transformers using oil insulation or in cables using solid insulation by the increase in the size of the device or in the transmission distance.
In order to improve the insulation reliability of the insulated device in its entirety, therefore, a variety of efforts have been made conventionally for appropriate design/manufacture of the device. For one improvement in the capacity of the power supply, confirmation and monitoring of the reliability of the entire device are required and various studies and investigations have been made.
One cause of the lowering of the insulation reliability is the non-uniform electric field. Especially, SF6 gas, used in the gas insulated device, exhibits an the especially excellent insulating characteristics in a non-uniform electric field, but the insulating characteristics drop extremely under the non-uniform electric field. The factors disturbing the field distribution in a gas insulating device can be defects such as flaws in the surface of high-voltage conductors or metal foreign matter having entered the inside during assembly or transportation. Other conceivable factors may be an imperfect contact of high-voltage conductors due to assembly mistakes or defects such as voids in the insulation spacer. If a non-uniform electric field is established in the gas insulating device by those defects, partial discharge may be caused during the operation, leading to a serious situation such as the breakdown of the entire circuit. This makes it necessary to detect partial discharge reliably before the entire circuit breakdown thereby to prevent such breakdown in advance. From this background, there have been examined methods for detecting partial discharge which may occur not only in a gas insulating device but also in any insulated device.
Of these, there is a method of detecting electromagnetic waves which are generated as a result of partial discharge, disclosed in Japanese Patent Laid-Open No. 107174/1989. By this method, there is provided a diagnosis system in which input signals containing many radio frequency band components, received by an antenna provided in an insulated device, are expanded in intensity for every frequency by a spectral analyzer, so that only the presence/absence of partial discharge is detected based on the distribution pattern and level. Another diagnosis system is disclosed in Japanese Patent Laid-Open No. 260868/1995, in which the presence/absence of partial discharge and the type of defect are judged from the distribution and intensity of such a spectrum such that period parameters such as the voltage phase angle are given to the intensity of a fixed frequency in the intensity spectrum expanded by the spectral analyzer.
An object of the present invention is to provide an insulated device diagnosing system and a partial discharge detecting method, which can detect partial discharge accurately even for a different structure and circuitry of a device, and for different place where partial discharge occurs.
In order to achieve the above-specified object, according to the present invention, there is provided an insulated device diagnosing system comprising: an antenna provided in an insulated device; a pattern generator for receiving a partial discharge signal from the antenna and preparing detection data such that periodic elements are given to a plurality of specific frequencies; a neuro computer or a finger printing method operation unit for operating the detection data prepared by the pattern generator; and a judgment unit for diagnosing the extent of abnormality, the deterioration, or the lifetime of the device from the operation result of the operation unit. Moreover, the distribution of the frequency components of the detection signal is also measured for specifying the specific frequencies to be detected. The insulated device is a gas insulated breaker, and when the partial discharge signals coming from a plurality of antennas provided at different positions in the gas insulated breaker are individually measured synchronously, the partial discharge is located from the spectral pattern of the detection data between the same frequencies or from the intensity ratio.
According to the present invention, moreover, there is provided a partial discharge detecting method comprising the steps of: inputting a partial discharge signal from an input terminal; preparing detection data which are given periodic elements at a plurality of specific frequencies of the partial discharge signal; and diagnosing the extent of abnormality, deterioration or lifetime of the device from the pattern or intensity of the prepared detection data.
There is further provided a partial discharge detecting method comprising the steps of: inputting a partial discharge signal from an input terminal; determining the intensity in which the partial discharge signal is expanded for each frequency by an FFT or a spectral analyzer to select a plurality of specific frequencies having high intensities, detecting the intensity of each frequency of the partial discharge signal to select a plurality of specific frequencies of which the intensities exceed a predetermined value, or selecting the frequency having the highest intensity from the plural specific frequencies; preparing detection data, which are given periodic elements at a specific frequency selected; and processing at least one of the detection data or displaying the same on a screen to detect the partial discharge.
There is further provided a partial discharge detecting method comprising the steps of: inputting a partial discharge signal from an input terminal; preparing detection data such that a plurality of specific frequencies of a partial discharge signal are given periodic elements; preparing sampling data by differentiating either averaged data averaged from detection data of different frequencies or known data from the respective detection data, or by differentiating the intensities of the detection data which are detected by antennas provided in different positions, between identical frequencies; and diagnosing the extent of abnormality, the deterioration or the lifetime of the device from the pattern or intensities of the prepared sampling data.
Moreover, the extent or kind of abnormality, the deterioration or the lifetime of the device is diagnosed by processing the detection data by a neuro or a finger printing method.